The present invention relates to a receiving apparatus having an outdoor receiving unit, a base station apparatus using the same, and a radio communication system.
The outdoor receiving unit is mainly used as a receiving unit in the base station apparatus, in the mobile communication, and installed on the receiving antenna pylon. In this case, in order to transmit a signal which is caught by a receiving antenna installed on the receiving antenna pylon to a main apparatus on the ground, a long coaxial cable or the like must be employed. Since the receiving signal is attenuated by the coaxial cable, NF (noise figure) is deteriorated. Therefore, there is such a subject that, even if a receiving apparatus with good performance is provided as the receiving apparatus installed on the ground, good receiving sensitivity cannot be achieved.
In such case, such an approach is often employed that a low-noise receiving amplifier is provided in the neighborhood of the receiving antenna as the outdoor receiving unit to suppress the degradation of NF by the coaxial cable and thus attain the good receiving performance.
However, a location on which the outdoor receiving unit is installed is a top of the pylon. Thus, since the failure due to the thunderbolt is often caused or the receiving sensitivity is degraded at the time of the failure, the operation of the outdoor receiving unit must always be monitored and also the failure, if occurs, must be quickly detected. Nevertheless, there is such a subject that, since the installing location is the top of the receiving antenna pylon, maintenance and inspection operations at that location are difficult.
Therefore, in order to overcome these subjects, approaches described in the following have been known. As the abnormality monitoring apparatus for detecting the abnormality such as gain reduction of the outdoor receiving unit, breakdown of the parts, etc. in the prior art, the pilot signal level monitoring apparatus disclosed in Patent Application Publication (KOKAI) Hei 5-122170 has been known. This apparatus injects the pilot signal from the input side of the receiving amplifier, and then detects the pilot signal component on the output side of the receiving amplifier to get the gain of the receiving amplifier.
Also, like the distributing/synthesizing system disclosed in Patent Application Publication (KOKAI) Hei 9-135125, such a method has been known that the pilot signal is injected from the distributor on the input side of the receiving amplifier and then the gain of the receiving amplifier is monitored by comparing the pilot signal got from the output of the synthesizer on the output side of the receiving amplifier with the reference value to detect the abnormal operation.
In addition, like the power supply current transmitting system disclosed in Patent Application Publication (KOKAI) Hei 7-177082, such a method has been known that the consumption current of the receiving amplifier is monitored and then the failure of the receiving amplifier is informed the main apparatus by changing the power supply current supplied to the outdoor receiving unit when the abnormality of the current value is detected.
However, there are subjects described in the following in the systems in the prior art. According to the pilot injection system, the abnormality is detected when the detected voltage of the pilot signal component is lowered. In this case, the outdoor receiving unit is decided as the failure even if the pilot signal generating means is broken down and thus the signal level is lowered. Therefore, there is such a subject that, when the abnormality is to be detected by the main apparatus on the ground, it cannot be discriminated which failure of the receiving amplifier, the pilot signal generating means, or the transmitting means causes the above abnormality.
Also, in the pilot signal generating means, unless a means for holding the output level of the pilot signal is provided, the output level is apt to change according to the change in the ambient temperature, the change in the power supply voltage, etc. Because of the influence of such change, the level of the pilot signal to be received in the main apparatus is changed even when the gain of the outdoor receiving unit is normal. In addition, there is such a subject that, since the gain of the receiving amplifier is measured by measuring the absolute value of the level of the pilot signal in the main apparatus, the gain of the main apparatus cannot be precisely measured unless the insertion loss of the transmitting means, which transmits the signal from the outdoor receiving unit to the main apparatus, is precisely measured in installing the outdoor receiving unit to correct the level.
Further, in the distributing/synthesizing system in the prior art, there is such a subject that, since the abnormality is detected in the outdoor receiving unit, a means for transmitting the abnormality detection signal must be provided so as to transmit the abnormality detection to the main apparatus.
Furthermore, at the time of the failure of the outdoor receiving unit, not only monitoring the consumption current but also monitoring the gain of the receiving amplifier is effective to quantitatively grasp a degree of degradation of the receiving sensitivity due to the failure. In the power supply current transmitting system in the prior art, there are such subjects that, when the abnormality of the current is detected in monitoring the consumption current of the receiving amplifier, a degree of deterioration of the gain of the receiving amplifier cannot be grasped and also, when the gain of the receiving amplifier is reduced due to disconnection of the signal line for coupling the multi-stage amplifiers, such reduction in the gain of the receiving amplifier cannot be detected.
Moreover, under the condition the outdoor receiving unit is broken down, it is desired that the radio system can be employed until the repair is completed. When the receiving amplifier of the outdoor receiving unit is composed of the multi-stage amplifiers, generally the degradation of the receiving sensitivity is increased in the case where the preceding-stage receiving amplifier is broken down rather than the case where the succeeding-stage receiving amplifier is broken down. For this reason, there is such a subject that, when the outdoor receiving unit is out of order, a degree of degradation in the quality of communication can be grasped by detecting at which stage the amplifier is broken by using the main apparatus, nevertheless such grasp of degradation cannot be achieved in the power supply current transmitting system.
Also, there is such a subject that, since a plurality of signal sources must be built in the outdoor receiving unit to get a plurality of pilot signals by the outdoor receiving unit, a method of obtaining the pilot signal is difficult.
Also, in the pilot injection system in the prior art, the level of the signal being input into the receiving means must be adjusted according to difference in the length of the cable as the transmitting means in installing the system. As the adjusting method, an amount of attenuation is set by 1 dB step, for example, by the stepwise attenuating means connected to the cable, in compliance with an amount of attenuation detected from the cable length. Therefore, as the error in correcting the insertion loss of the cable, the error of xc2x10.5 dB is produced at maximum. As a result, there is such a subject that, in detecting the gain reduction, the detection precision is degraded owing to the influence of such error.
Also, if the failure detecting portion in the main apparatus is out of order, it is sometimes decided that the receiving amplifier has been broken down in the receiving unit which detects the abnormality of the outdoor receiving unit by detecting the pilot signal. Therefore, there is such a subject that, even if the amplifier of the outdoor receiving unit is normally operated and thus no degradation of the quality of communication is caused, such situation can be detected as the abnormality of the outdoor receiving unit.
Also, in the configuration that the level of the pilot signal is detected in the main apparatus to detect the abnormality of the outdoor receiving unit, there is such a subject that, since the block for measuring the level of the pilot signal must be newly equipped, a size of the configuration is increased.
In addition, unnecessary signals in reception are input by injecting the pilot signal. Therefore, assume that the frequency of the pilot signal is set as fp(=f0+xcex94f) where f0 is the frequency of the receiving signal, for example, if the interference wave fud(=f0+2xc3x97xcex94f) is input externally, the receiving signal f0 can be given by
2xc3x97fpxe2x88x92fud=2xc3x97f0+2xc3x97xcex94fxe2x88x92f0xe2x88x922xc3x97xcex94f=f0.
As a result, there is such a subject that sometimes the intermodulation distortion is caused.
Further, in the pilot injection system in the prior art, if the abnormality of the outdoor receiving unit is detected in the main apparatus, the reference voltage with which the detected voltage of the pilot signal component being detected in the main apparatus is compared must be adjusted due to variation in the attenuation amount of the transmitting means. At that time, such adjusting operation must be conducted manually to satisfy the specified value conditions by using the measuring tool such as the tester, etc. As a result, there is such a subject that operability is not good, e.g., the read error of the measuring tool is caused in adjusting, the external measuring tools are needed, etc.
Furthermore, the level of the pilot signal which is superposed on the cable which transmits the receiving signal being amplified in the outdoor receiving unit to the main apparatus must be corrected in installing the outdoor receiving unit. However, there is such a subject that, if such adjustment is conducted manually, adjust error due to the read error of the measuring tool or manual adjust error such as inputting of the false adjust value may happen.
Moreover, owing to the variation of the internal voltage of the pilot signal level monitoring portion, the reference voltage with which the detected signal of the pilot signal is compared and the voltage used to detect the abnormality are varied every receiving apparatus. Therefore, there is such a subject that the accuracy of the abnormality detection is lowered in detecting the abnormality.
Still more, in the abnormality detecting means in the prior art, the system must be operated as it is under the situation the abnormality has been detected until the defected system can be repaired. Hence, there is such a subject that, if the abnormality is detected at the time of the failure occurring, the communication area is narrowed.
The present invention has been made to overcome the subjects in the prior art, and intends to improve reliability and precision of detecting abnormality of a receiving amplifier.
The present invention provides the receiving apparatus which comprises the outdoor receiving unit, the main apparatus, and the transmitting means for transmitting the receiving signal from the outdoor receiving unit to the main apparatus. Since the first and second pilot signals having a different frequency respectively are injected into the input and the output of the receiving amplifier in the outdoor receiving unit and then relative values of the levels of the first and second pilot signals are measured in the main apparatus, the gain of the receiving amplifier can be measured precisely.
Also, since the first and second pilot signals having a different frequency respectively are injected into the inputs of two receiving amplifiers connected in parallel with the outdoor receiving unit and then relative values of the levels of the first and second pilot signals are measured in the main apparatus, the gain of the receiving amplifier can be measured precisely.
In addition, since n+1 pilot signals having a different frequency respectively are injected into n-stage receiving amplifiers in the outdoor receiving unit and then levels of the n+1 pilot signals are measured in the main apparatus, the gain of the receiving amplifier can be measured precisely and also the location where the fault of the n-stage receiving amplifiers is caused can be detected.
Further, n pilot signals of the outdoor receiving unit are generated by multiplexing means having different n-stage multiples, a plurality of pilot signals having a different frequency respectively can be obtained with a simple configuration.
Furthermore, since the current of the receiving amplifier in the outdoor receiving unit is measured and then the frequency of the pilot signal is set based on such information, the current value of the receiving amplifier can be monitored precisely.
Moreover, since the currents of plural receiving amplifiers in the outdoor receiving unit are measured and then the frequency of the pilot signal is set based on such information, the current values of plural receiving amplifiers can be monitored precisely.
Still more, since the levels of the receiving signal at the input and the output of the receiving amplifier in the outdoor receiving unit are compared/measured and then the frequency of the pilot signal is set based on such information, the gain of the receiving amplifier can be measured precisely and also the location where the fault is caused can be detected.
Also, the level of the receiving signal at the input of the receiving amplifier in the outdoor receiving unit is amplified by the amplifier which has the same gain and noise figure as the receiving amplifier and then compared with the level of the receiving signal at the output of the receiving amplifier to measure, and then the frequency of the pilot signal is set based on such information. Therefore, the gain of the receiving amplifier can be measured precisely even if the input level of the receiving signal is low and also the location where the fault is caused can be detected.
Also, the first and second pilot signals having different phase respectively are injected into inputs of two receiving amplifiers connected in parallel with the outdoor receiving unit such that amplitudes of two pilot signals can be canceled by the synthesizing means. Therefore, unnecessary spurious components by the pilot signals are not input into the main apparatus in the normal operation of the receiving amplifier, and thus the good receiving characteristic can be achieved.
Also, the first and second pilot signals having different phase respectively are injected into the input and the output of the receiving amplifier in the outdoor receiving unit such that amplitudes of two pilot signals can be canceled by the adding means. Therefore, unnecessary spurious components by the pilot signals cannot be input into the main apparatus in the normal operation of the receiving amplifier, and thus the good receiving characteristic can be achieved.
Also, since the first and second pilot signals having different phase respectively are added or synthesized to have predetermined different amplitudes, unnecessary spurious components by the pilot signals can be reduced in the main apparatus in the normal operation of the receiving amplifier and also the location where the fault is caused can be detected.
Further, since the level holding circuit for holding the level of the pilot signal at a predetermined level is provided to the outdoor receiving unit, the gain of the receiving amplifier can be measured precisely.
Also, the level of the pilot signal amplified by the receiving amplifier is detected and measured in the outdoor receiving unit, and then the frequency of the pilot signal is set based on such information. Therefore, the gain of the receiving amplifier can be measured precisely and also the location where the fault is caused can be detected.
Also, the level of the pilot signal amplified is detected and measured in the outdoor receiving unit and also the consumption current of the receiving amplifier is measured, and then the frequency of the pilot signal is set based on such information. Therefore, the gain of the receiving amplifier can be measured precisely, and the location where the fault is caused can be detected, and also the current value of the receiving amplifier can be monitored precisely.
Further, the pilot signal input into the receiving amplifier in the outdoor receiving unit and the pilot signal output therefrom are branched and added such that their phase differences become 180 degree, then the added output level is detected and measured in the outdoor receiving unit, and then the frequency of the pilot signal is set based on such information. Therefore, the gain of the receiving amplifier can be measured precisely, and also the location where the fault is caused can be detected.
Furthermore, since an amount of attenuation of the variable attenuating means in the main apparatus is controlled based on the result of the level detection of the pilot signal, an amount of loss of the transmitting means can be automatically compensated.
Moreover, since the level detecting means for the pilot signal in the main apparatus can be used commonly with the level detecting means for the receiving signal by switching the local oscillation frequency, an amount of loss of the transmitting means can be automatically compensated with a simple configuration.
Still more, since the level detecting means for the pilot signal is provided in the main apparatus and the level of the pilot signal can be detected by switching the local oscillation frequency, the fault of the abnormality detecting means can be detected.
Also, in the TDD system receiving apparatus, the level detecting means for the pilot signal in the main apparatus can be employed commonly with the level detecting means for the receiving signal by switching the local oscillation frequency, and also the level of the pilot signal can be detected within the time interval during when the receiving operation is not carried out. Therefore, the abnormality of the pilot signal can be detected with a simple configuration.
Further, there are provided the reference voltage adjusting means for adjusting the level of the reference voltage which is compared with the level detected result of the pilot signal in the main apparatus, and the reference value sensing portion for sensing that the compared result is within the standard range. Therefore, an amount of loss of the transmitting means can be compensated without its precise measurement and thus the abnormality of the pilot signal can be detected precisely.
Furthermore, the reference voltage adjusting means for adjusting the level of the reference voltage which is compared with the level detected result of the pilot signal in the main apparatus and also the error amplifying portion for amplifying the error of the compared result are provided, and also the reference voltage value can be adjusted by the adjusting device which has the controlling means for outputting the control signal of the reference voltage. Therefore, compensation of the amount of loss of the transmitting means can be adjusted simply.
Moreover, since the reference voltage of the adjusting device is set based on the power supply voltage of the main apparatus, the compensation of an amount of loss of the transmitting means can be adjusted simply with no influence of the error of the power supply voltage
Further, since an amount of attenuation of the variable attenuating means can be controlled to the lowest minimum when the abnormality of the pilot signal is detected in the main apparatus, reduction in the receiving characteristic can be suppressed at the time of the fault.
In addition, since the base station apparatus having the receiving apparatus is provided, the fault detection and the adjustment of the transmitting means can be performed precisely with a simple configuration.
Still more, since the radio communication system having the receiving apparatus and the base station apparatus is provided, reduction in the communication area can be suppressed at the time of the failure.